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Message-ID: <20250510145449.4117af82@pumpkin> Date: Sat, 10 May 2025 14:54:49 +0100 From: David Laight <david.laight.linux@...il.com> To: Ard Biesheuvel <ardb+git@...gle.com> Cc: linux-kernel@...r.kernel.org, x86@...nel.org, Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [RFC PATCH 2/3] x86/boot: Set __pgtable_l5_enabled correctly before calling into C code On Tue, 6 May 2025 17:45:35 +0200 Ard Biesheuvel <ardb+git@...gle.com> wrote: > From: Ard Biesheuvel <ardb@...nel.org> > > Ensure that __pgtable_l5_enabled() is set to its permanent value before > calling into any C code that may manipulate page tables or reference any > global variable or object that may be dimensioned differently based on > whether 5-level paging is in use. ... > #ifdef CONFIG_X86_5LEVEL > -/* __pgtable_l5_enabled needs to be in .data to avoid being cleared along with .bss */ > -unsigned int __section(".data") __pgtable_l5_enabled; > +unsigned int __pgtable_l5_enabled = 1; > + > +/* These need to be in .data to avoid being cleared along with .bss */ > unsigned int __section(".data") pgdir_shift = 39; > unsigned int __section(".data") ptrs_per_p4d = 1; Is that comment (and the section assignment) relevant given that they are initialised non-zero? I'd guess that __pgtable_l5_enabled was getting set before .bss was cleared? David
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